Field of the Invention
This invention relates to an improved concrete, and in particular to what can be characterized by a polymer concrete in which a monomer polymerized in situ is used as the binder component for the concrete aggregate instead of conventional hydraulic binders which require the addition of water to set.
More specifically, the present invention relates to a polymer concrete free of water in which the polymeric binder comprises furfuryl alcohol monomer polymerized in situ with the aid of an acid catalyst.
Generally, a significant proportion of concrete used today in pavements, structural supports for buildings and machinery and other widely known uses is formed from a mixture of fine and coarse mineral aggregates and a paste of Portland cement and water. Such Portland cement formulations comprise from about 60% to 75% aggregates and from about 25% to 40% paste by volume of the formulation. The quality of Portland cement concrete depends on many factors including the type of aggregate used and gradation of the aggregate size as well as the quality and availability of the paste and the amount and quality of the water relative to the amount of Portland cement added.
Studies and tests have been performed on polymeric additives to concrete and polymeric materials used as substitutes for the typical hydraulic cement binder materials. For example, polymer cement concrete which is a mixture of conventional hydraulic cement concrete and high molecular weight polymers has been formed comprising generally thermoplastic or rubber polymers which are added as emulsions or dispersions to the hydraulic concrete mix. Polymers which have been utilized in such systems include polyvinylacetate, polyacrylates, polyvinylchloride, styrene-butadiene and polyvinylidenechloride. Copolymers of two or more of the polymers have also been utilized. While improvements in the physical properties such as compressive strength, bending strength and decreased water permeability have been reported in the literature for these polymer cement concretes, these improvements have been offset by significant dimensional shrinkage. It has been found that the wear-resistance of polymer cement concretes is significantly better than Portland cement concrete and thus, polymer cement concretes have found some use as floor and deck coverings in public buildings, industrial plants and bridges.
Over the last fifteen years, extensive laboratory studies have been performed in the United States on both polymer-impregnated concrete and polymer concrete in which the hydraulic binder is totally substituted with a polymeric material. Such studies have primarily focused on solving problems on failing concrete bridge decks and on concrete pipe in corrosive waste water environments. Polymer-impregnated concrete consists of polymer-impregnation of Portland cement concrete with a low viscosity monomer that is subsequently polymerized in situ. The monomer penetrates the concrete matrix to a finite depth (sometimes controlled) and is subsequently polymerized by heat, catalysts, or radiation. Significant property improvements in compressive strength (285%) tensile strength (292%), modulus of elasticity (80%), freeze-thaw durability (300%) and water permeability have been reported by U.S. Department of Interior/Bureau of Reclamation, W. C. Cowan & H. C. Riffle Investigation of Polymer-Impregnated Concrete Pipe, September, 1974. Data on the resistance of polymer-impregnated concrete to mild hydrochloric and sulfuric acids and permeation by chloride was presented by the Brookhaven National Laboratory in 1976, L. E. KuKacka and M. Steinberg Concrete-Polymer Composites, A Material For Use In Corrosive Environments, March, 1976.
Polymer concrete differs from typical Portland cement concrete, polymer cement concrete and polymer-impregnated concrete. Polymer concrete contains no cement or water. The development of physical and chemical properties of polymer concrete depends entirely on the chemical and slightly physical reaction between the polymeric binder, hardener and the aggregate system. Most of the early experimentation on polymer concrete has occurred in Eastern Europe and the Soviet Union. More recent experimentation in the United States has focused on bridge deck and highway repairs and experimental attempted use of a polymer concrete lining for steel pipe in geothermal applications. Few commercial applications of polymer concrete are known, but experimental use of polymer concrete materials has been ongoing since about 1960. For example, in bridge deck and geothermal applications, polymer concrete systems containing methylmethacrylate and blends of polyester/styrene have been evaluated and their properties have been measured and reported by G. W. DePuy, L. E. KuKacka, Concrete-Polymer Materials, Fifth Topical Report, Brookhaven National Laboratory, December, 1973. Significant improvements in compressive strength (18-20,000 PSI) water absorption (less than 1%) and chemical resistance are obtained versus conventional Portland cement concretes. However, for applications in heavy industrial environments, even more chemically resistant polymer concretes are needed.
The present invention provides a polymer concrete with improved physical properties over conventional Portland cement concretes and which can be used for a wide variety of uses such as coatings, coverings, repairs and for applications in heavy industrial environments in which strength, flexibility and chemical resistance are required. It has been found that furan resins, particularly those formed from furfuryl alcohol monomers can be mixed with a novel aggregate system to yield polymer concretes of improved chemical and physical characteristics. Furan polymers have found wide use in the formation of foundry cores in which small-sized aggregates (sand) are mixed therewith, all large-sized aggregates being excluded from such formulations. Likewise, there have been studies performed on polymer concrete systems including polymer concrete systems utilizing furan polymers in the United States, such as by the U.S. Atomic Energy Commission, Oak Ridge National Laboratory, Oak Ridge, Tenn., Translation Series AEC-tr-7147, November, 1971, and further testing on furan polymer concretes in the Soviet Union in which it was found that the performance of polymer concretes are significantly influenced by aggregate selection to produce furan polymer concretes with a range of compressive strengths varying from 5000 to 15,000 PSI; I. M. Elshin, Scientific Research Institute of Hydrotechnics, Kiev, U.S.S.R., "Experience in Using Plastic Concrete with Furan Resins in Different Structures". Likewise, Sneck, Tenho, Marttiner, Pertti, Eneback, and Carl, The State Institute for Technical Research, Otamiemi, Finland, A Preliminary Investigation on the Properties of Some Fufural Acetone Resin Mortars, have tested various physical properties of furan polymer concretes as has The Quaker Oats Company, Chemical Division, Chicago, Ill.